The present invention relates to an adjustable reservoir for rod-like articles, such as smoking articles and filter rods for smoking articles.
It is common to use one or more reservoirs on a production line that fabricates smoking articles such as cigarettes, to absorb a temporary excess and make up a temporary deficit in the quantity of units produced if the speed of part of the production machinery varies with respect to that of adjacent units. For example, if a particular machine breaks down or has to be stopped, it is necessary to temporarily store units produced by the upstream machine until the machine in question is operational again and can process the stored units. Similarly, if the upstream machine goes out of service, units stored in a reservoir can be processed by the downstream machine until the upstream machine is able to supply units again. The reservoir acts as a storage buffer between the machines. Reservoirs may be employed between a machine that makes filter rods and a machine that assembles cigarettes from filter rods and tobacco rods to store the filter rods, or between the cigarette maker and a packing machine to store the cigarettes, for example.
Usefully, reservoirs have a variable capacity to accommodate changes in the volume flow of units along the production line. Such reservoirs may comprise an arrangement of one or more conveyors that form a variable length conveying path between adjacent machines The path is made long if the upstream machine is producing more units that the downstream machine can process, to accommodate more units, and shortened if both machines are operating at the same speed to minimise the path between the machines and hence minimise production time. Reservoirs that provide a path between machines are known as first-in, first-out (FIFO) reservoirs, because the first unit delivered into the reservoir from the upstream machine is also the first unit output by the reservoir to the downstream machine.
Alternatively, a reservoir may be a last-in, first-out (LIFO) reservoir, in which the most recently stored units are delivered first to the downstream machine. This may be achieved by a conveyor that branches off from the production line, and runs in a forward direction to take units from the line and in a reverse direction to deliver units back to the line.
A problem with LIFO reservoirs is that the units delivered into the reservoir first may stay in the reservoir for an extended period before being processed further, since the more recently delivered units are processed first. The time for which each unit stays on the production line depends on its location in the reservoir, and the order in which units are processed by the downstream machine is different from the order in which units are produced from the upstream machine. This makes it very difficult to track individual units. However, the requirement for product tracking and traceability is becoming more widespread in many production industries, including the tobacco industry. Use of LIFO reservoirs is incompatible with this.
A further issue with LIFO reservoirs relates to the freshness of the product, if the reservoir is not exhausted regularly. For long production runs in the tobacco industry, units could be up to two weeks old before they leave the reservoir, which is undesirable for cigarettes and the like.
Consequently, FIFO reservoirs are becoming the preferred option. However, commonly used FIFO reservoirs such as those described in EP 1,344,463, EP 1,445,218, WO 02/085144 and WO 2004/085293 typically occupy a very large area. These devices comprise an input, an output and a single endless conveyor divided into an active branch extending from the input to the output that acts as the reservoir, and a return branch from the output to the input, where the capacity of the reservoir is altered by varying the lengths of the two branches in a complementary manner, such as by moving a drum around which the conveyor is wound. The large footprint of these FIFO reservoirs frequently means that they can only be incorporated into an established production system by mounting them above the production machinery. This requires a very large ceiling height, typically in excess of 7 meters, which is often not available in existing factories.
US 2003/0000811 describes an alternative FIFO reservoir that is intended for use with cigarette packets. The reservoir comprises a stack of circular conveyors that each rotate in the same direction and which are connected in series by linking means joining each conveyor to the one below to give a continuous path from an input at the top of the stack to an output at the bottom. The capacity is adjusted by varying the speed of the individual conveyors to change the spacing between packets as they are delivered to a conveyor.